The hex color #3fff00 is a light color. The web-safe version is Hex
#33FF00. A complementary color is
#C000FF. The grayscale version is
#6A6A6A. A 20% lighter version of the original color is
#72FF33, and Hex
#0CCC00 is the 20% darker color. If the color is saturated by 10%, you get
#3BFF00. If the color is desaturated by 10%, the color
#43F00B is obtained.